水稻—土壤界面Fe、Mn、As耦合及其阻控As迁移机制的研究

It is reported that rice （Oryza sativa L.）is much more efficient in assimilating arsenic into grain than other staple cereal crops, and consumption of rice constitutes a large proportion of dietary intake of arsenic, especially inorganic arsenic. Therefore, how to minimizing arsenic bioavailability and its concentration in rice grain has attracted worldwide attention. While the rice-soil interface is a special property of microenvironment, and plays an important role for changing arsenic fractionation in soil and transferring arsenic from soil to rice. Moreover, the interaction between iron, manganese and their oxides and heavy metal ions in the rice-soil interface is study focus for soil chemistry and environmental chemistry. Therefore, it is very important and necessary to study the relationships between the characteristics of rice roots, rhizosphere environment and environmental factors to control arsenic transfer from soil to rice, especially to polished rice. In our study, the arsenic-contaminated paddy soil collected from Hunan province will be employed. There are three kinds of experiments such as hydroponic experiment, pot experiment and field experiment. The aims are to study the fractionations changes, bioavailabilities, and influencing mechanisms of iron, manganese and arsenic in rice –soil interface, even arsenic uptake by rice; to study micromechanics of the coupled roles of iron, manganese and arsenic in rice –soil interface under different conditions such as water management, dissolved oxygen, microorganism. Further, It is to study to mechanisms of reduce arsenic accumulation in rice by the cooperation between rhizoshere of rice, soil solution, iron and manganese and their oxides, and microorganism. Our results will provide scientific guidance for remediation of arsenic polluted-paddy soil and mitigation excessive arsenic accumulation in rice.

水稻砷污染已成为当今全球环境热点问题之一。由于水稻—土壤界面是一个性质特殊的微域环境，能够影响土壤砷的形态变化以及向水稻迁移，且土壤中铁和锰及其氧化物与重金属离子的相互作用是土壤化学和环境化学研究的重点。因此，通过研究水稻根系特性、根际环境和环境因子等之间的关系来阻控土壤砷向水稻体内的转移，尤其是向稻米的迁移至关重要。本项目通过采集砷污染土壤，将水培实验和盆栽实验、大田实验相结合，探究在水稻—土壤界面铁、锰、砷相互之间的形态变化及其作用机制，以及对水稻吸收砷的影响；运用先进技术如核磁共振技术，探究水稻—土壤界面中铁、锰、砷耦合及相互作用的微观机理，探究环境因子如水分、溶解氧、微生物等对水稻—土壤界面铁、锰、砷耦合的影响；进一步探究利用水稻根际、土壤溶液和铁锰及其氧化物来阻控砷向水稻体内的转移机理，为发展土壤砷污染控制技术提供理论依据。

本项目结合了我国南方地区稻田砷污染防控方面的重大现实需求以及国际科研界在水稻-土壤界面元素相互作用的前沿领域，主要研究了砷-铁-锰元素在土壤以及水稻根系微域环境的动态响应过程及驱动因子；以及利用铁锰砷的动态响应关系来阻控土壤砷向水稻体内的转移。本项目结合土壤培育实验（外源铁锰）及盆栽实验，探究砷在单一土壤体系以及水稻-土壤复合体系内的动态迁移转化过程。利用一系列的实验手段揭示了砷在单一土壤体系下的固-液分配规律及驱动因子；通过土壤培育实验分别探明了外源含铁、锰物质对土壤中砷的形态转化的影响；揭示了水分管理模式影响土壤中砷的动态转化规律；同时，基于铁锰元素对砷在土壤体系的固-液分配的影响的驱动因子，探讨了外源铁锰物质阻控水稻砷富集的过程及关键环境因子。此外，结合砷在土壤-水稻界面与铁锰元素的动态反应过程，建立了水分管理模式-耦合添加外源铁锰的措施，并将其应用到了实际土壤体系。本项目的主要研究成果包括（1）矿山农田土壤中砷的迁移与转化规律及驱动因子；（2）不同外源铁锰物质影响水稻土壤中砷的固-液分配的动态过程及机制；（3）铁锰氧化物阻控水稻富集砷的机制及过程；（4）不同水分管理模式驱动土壤无机砷迁移转化的规律及响应因子；（5）不同水分管理模式耦合外源铁锰阻控水稻砷富集的过程。本项目成果深入揭示了水稻-土壤体系内铁、锰、砷的动态互作过程，提高了对环境因子扰动下重金属环境行为的理解，为发展砷污染控制技术提供了理论依据，对指导环境修复和环境风险评价工作具有重要意义。